Polyurethane adhesives and coating compositions

ABSTRACT

ADHESIVES AND COATING COMPOSITIONS COMPRISE A SOLUTION OF A HYDROXYL-TERMINATED URETHANE PREPOLYMER AND AN ISOCYANATE-TERMINATED URETHANE PREPOLYMER IN WATER.

United States Patent 3,730,927 POLYURETHANE ADHESIVES AND COATINGCOMPOSITIONS Hans R. Schloss, Wallington, N.J., assignor to Sun ChemicalCorporation, New York, N.Y.

No Drawing. Continuation-impart of application Ser. No. 29,306, Apr. 16,1970, now Patent No. 3,666,835, dated May 30, 1972. This applicationMar. 7, 1972, Ser. No. 232,611 The portion of the term of the patentsubsequent to May 30, 1989, has been disclaimed Int. Cl. C08g 51/22,41/04 U.S. Cl. 26029.2 TN 10 Claims ABSTRACT OF THE DISCLOSURE Adhesivesand coating compositions comprise a solution of a hydroxyl-terminatedurethane prepolymer and an isocyanate-terminated urethane prepolymer inWater.

This application is a continuation-in-part of copending application S.N.29,306 (filed Apr. 16, 1970) now U.S. Pat. No. 3,666,835 (issued May 30,1972).

This invention relates to novel adhesives and coating compositionscomprising water solutions of polyurethanes. More specifically theinvention relates to the use of novel polyurethane systems as textilelaminating adhesives and as coating compositions.

Fabric-to-fabric bonding is an important feature in the textile field,particularly in the area of clothing. It permits, for example, built-inlinings in garments, more stable structures, greater wrinkle resistance,improved stretch and recovery, more attractive appearance, greatercomfort, and hitherto unattainable surface effects. Polyurethanes areparticularly desirable as adhesives for bonded fabrics because they haveextraordinary chemical resistance, especially solvent resistance;abrasion resistance; laminating qualities; and handling properties.

There are, however, a number of major disadvantages to the use of knownpolyurethane adhesives and coatings. Cloth laminated with polyurethanestends to yellow upon exposure to light; the materials which are to bebonded together have to be heated to high temperatures and maintained atthese high temperatures in order to cure the adhesive and obtain asatisfactory bond; moreover, adhesives and coating compositions areusually applied as a solution in a solvent which generally is highlyflammable and often toxic.

It has now been found that these difliculties can be overcome by thecompositions of the present invention which comprise a solution of twoprepolymers, namely a hydroxyl-terminated urethane prepolymer (A) and anisocyanate-terminated urethane prepolymer (B), in water. Prepolymer A isin general the product of the stepwise reaction of (a) an alkyleneoxide-based polyol capped on both ends with ethylene oxide with (b) anisocyanate and (c) a glycol in the presence or absence of (d) a polyolhaving a functionality of at least 3 and/or (e) a catalyst. Prepolymer Bis formed by reacting (f) a straight chain glycol or polyol with (g) apolyol having a functionality of at least 3 and (h) an isocyanate in thepresence or absence of a catalyst.

PREPOLYMER A The polyols (a) are prepared by adding an alkylene oxide tothe two hydroxyl groups of an alkylene glycol 3,730,927 Patented May 1,1973 nucleus. The resulting water-insoluble base can be made to anycontrolled length ranging in molecular weight from about 800 up toseveral thousand. For the purpose of this invention, the molecularweight is generally within the range of about 950 to 3000, andpreferably about 1400 to 2400. Ethylene oxide is then added to thishydrophobic base to put water-soluble polyoxyethylene groups onto theends of the molecule. The resulting condensates, such aspolyoxyethylenepolyoxypropylene glycol, are obtainable commercially,e.g., Pluronics sold by Wyandotte Chemicals Corp. and Niax Polyol LCsold by Union Carbide Corporation.

The condensate is then reacted with an excess of any aliphatic,aromatic, or cycloaliphatic compound of the general formula R(NCX),, inwhich R is a polyvalent organic radical, X is oxygen or sulfur, and n isany integer except zero, provided that any such compound contains nosubstituent which will interfere with the reaction. Examples ofisocyanates and isothiocyanates are polymethylene diisocyanates anddiisothiocyanates, such as ethylene diisocyanate, trimethylenediisocyanate, tetramethylene diisocyanate and pentamethylenediisocyanate; and the corresponding diisothiocyanates; alkylenediisocyanates and diisothiocyanates, such as propylene-1,2-diisocyanate, butylene 1,2 diisocyanate, butylene-l,3-diisocyanate,butylene-2,3-diisocyanate, and butylene-l,3-diisothiocyanate; alkylidenediisocyanate and diisothiocyanates, such as ethylidene diisocyanate,butylidene diisocyanate and ethylidene diisothiocyanate; cycloalkylenediisocyanates and diisothiocyanates, such ascyclopentylene-l,3-diisocyanate, cyclohexylene-1,4-diisocyanate andcyclohexylene-l,2-diisothiocyanate; cycloalkylidene diisocyanates anddiisothiocyanates, such as cyclopentylidene diisocyanate,cyclohexylidene diisocyanate and cyclohexylidene diisothiocyanate;aromatic diisocyanates and diisothiocyanates, such as metaphenylenediisocyanate, paraphenylene diisocyanate, l-methyl-2,4-phenylenediisocyanate, diphenyle'ne-4,4-diisocyanate or p-phenylenediisothiocyanate; aliphatic-aromatic diisocyanates or diisothiocyanates,such as xylylene-1,4-diisocyanate, xylylene- 1,3-diisocyanate, 4,4diphenylenemethane diisocyanate, 4,4-diphenylene-propane diisocyanate,xylylene-1,4-diisothiocyanate or durene diisocyanate. Aromaticdiisocyanates, for example, a tolylene diiscoyanate or isomeric mixturesthereof, are preferred.

The resulting NCO-terminated compound is further reacted with anysuitable glycol in order to build up the polymer and to give it hydroxyltermination, thus increasing the dry-cleaning resistance and thewater-solubility of the product. Sufficient diisocyanate should be usedin making the NCO-terminated compound that the ratio of NCO groups tothe total OH groups provided by the condensate and the glycol will beabout 0.88-0.97. In general the addition of the glycol enables one totailor the polymer to effect the desired physical properties for thefinal end use; for example, with ethylene glycol the product is stiff,hard, and brittle; with tetraethylene glycol the product is softer andmore flexible. Furthermore, the addition of short chain glycolsmultiplies the number of urethane linkages, thus increasing the numberof polar groups per molecule. In this manner functional groups can beadded that will affect the water solubility or insolubility of theproduct, its resistance to dry cleaning, its flame resistance orfireproofing qualities, and the like.

Such glycols as ethylene glycol, diethylene glycol, triethylene glycol,tetraethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol,tripropylene glycol, tetrapropylene glycol, 1,3-butanediol,1,4-butanediol, 1,6-hexanediol, thiodiglycol, and the like, and mixturesthereof have been found suitable. The amount of glycol may range up toabout 8.0 equivalents per equivalent of the condensate, and preferableabout ll-S to 2.5 equivalents.

If desired, this OH-terminated product may further be reacted with apolyol which has a functionality greater than two. The polymer moleculeshould have long portions or sections of chain with no intermolecularforces or crosslinks for elasticity (a); the introduction of urethanelinkages in portions of the chain increases moistureandsolvent-resistance and increases intermolecular forces to effect highermodulus, tear strength, hardness, melting point, and glass transitiontemperatures (b); the crosslink points hold the chains together forsolventand moisture-resistance, as illustrated below:

The polyol may be any suitable polyhydric alcohol having about to 6hydroxyl groups and a molecular weight less than 500, provided that itdoes not contain any tertiary N atoms. Suitable compounds include, butare not limited to, glycerine, trimethylolpropane, triethylolpropane,pentaerythritol, 1,2,4 butanetriol, 1,2,5 pentatriol, 1,2,6-hexanetriol,sucrose sorbitol and the like and mixtures thereof. A polyhydric alcoholhaving hetero oxygen or sulfur atoms in the chain may also be used. Theamount of polyol employed may range from about 0.05 to 1 equivalent,preferably about 0.15 to 0.35, per equivalent of the condensate.

The resulting hydroxyl-terminated prepolymer is characterized by being aclear-liquid, water-white to light amber in color, having a lowviscosity and a molecular weight within the range of about 3500 to60,000.

Although a catalyst is not required in the preparation of Prepolymer A,the use of such a compound may be desired to accelerate the reaction.Particularly suitable are the amines, such as tetramethylbutane diamine,triethylamine, diethylcyclohexylamine, dimethyldodecylamine,dimethyloctadecylamine, dimethylstearylamine, N- ethylmorpholine,triethylene diamine, tripropylamine, tributylamine, triamylamine,tribenzylamine, dimethylaniline, tetraethylene diamine, and the like,and mixtures thereof. The amines may be employed in an amount rangingfrom about 0.05 to 2.0 percent by weight, based on the total weight ofthe hydroxyl-terminated compound.

Other suitable catalysts are the organometallic compounds, such as forexample dibutyltin diacetate, dibutyltin dilaurate, dibutyltindi-2-ethylhexoate, stannous octoate, stannous oleate, stannous2-ethylhexoate, and the like, and mixtures of these. In general theseare used in an amount ranging from about 0.005 to 0.03, preferably 0.01to 0.02, weight percent, based on the total weight of the compositions.

Although the method of preparing Prepolymer A is critical, it ispreferred to react the condensate with the isocyanate compound beforereacting it with the glycol and the polyol. When the ratio of NCO groupsto OH groups is about 1, the compound tends to form a gel. To reduce toa minimum the conditions favoring the gel, it is preferred to go from anexcess of NCO groups to an excess of OH groups, thus passing only oncethe critical point where they are equal, than to go from an excess of OHgroups to an excess of NCO groups and back to the required excess of OHgroups, passing twice the point at which the two are equal and extracare must be taken.

The reaction normally takes place at room temperature but may beaccelerated by heating the reactants to about 40 C. to 150 C. Anysuitable apparatus may be used for mixing the ingredients together.

PREPOLYMER B r The NCO-terminated prepolymer is prepared by reacting (f)a straight chain glycol with (g) a polyol having a functionality of atleast 3 and (h) an isocyanate in the presence or absence of a catalyst.The glycol (f) preferably has a molecular weight between about 62 and800 and may be any suitable glycol such as one of the glycols set forthabove. The isocyanate may be any suitable aliphatic, aromatic, orcycloaliphatic compound having the general formula R(NCX),, as definedabove. The polyol (g) and the catalyst, if desired, likewise may be oneof those set forth above. The ratio of the reactants may range fromabout 3 to 6 parts of the glycol: 20 to 60 parts of isocyanate: 4 to 40parts of polyol (g), and preferably 3 to 5:40 to 60:10 to 15. Theresulting prepolymer is characterized by low viscosity and has amolecular weight in the range of about 300 to 1600. In general practicethe two prepolymers are inter-reacted in an amount ranging from about 10to about 60 parts of Prepolymer B per parts of Prepolymer A. PrepolymersA and B are combined by any known and convenient means, e.g., bystirring or shaking. The resulting system is applied to the substrate orsubstrates by any conventional coating technique.

Although the compositions may be applied as 100% solids, there are-somedifiiculties involved. The materials are highly viscous, and handlingand processing may be problems. Accordingly, it has been foundadvantageous to use the polyurethane compositions in solution in water,thus lowering their viscosity, making it easier to process and handlethe compositions and to aply them to substrates in uniform thin films.In addition, it is easier to incorporate such conventional materials asfillers, colorants, and the like into the adhesive or coatingcomposition when it is in solution in Water than when it is 100% solids.

In general the compositions of this invention consist of about 40 to 90,preferably about 50 to 85, percent of the polyurethane (Prepolymer APlus Prepolymer B) and about 10 to 60, preferably about 15 to 50,percent of water.

The polyurethane resin compositions prepared in the above-describedmanner have many unexpected properties which are superior to those ofconventional polyurethane products for many applications. The compoundsof this invention are particularly suitable as adhesives forfabricto-fabric bonding, such as cotton, rayon, wool, nylon, polyester,acrylic, polyamide, polyurethane, polyolefin, metallized fabric, and thelike, and blends thereof, where the two bonded fabrics may be the sameor different. They are also useful for laminating plastic film toplastic film or to other substrates; in fabric coating; in papercoating; and the like.

The new polyurethanes are completely non-yellowing. They cure below 100F., rather than at the conventional curing temperature of about to F.,and can be applied as 100% solids or in water-solution. The absence of asolvent (other than water) means that employing the materials of thisinvention in a laminating or coating process eliminates the need forventilation and for special explosion-proof equipment; there is no odorand no problem of air pollution. In addition, the polyurethanes of thisinvention are more resistant than conventional fabric-bonding adhesivesto dry cleaning, washing, and abrasion. They are easily applied to avariety of substrates and can be tailor-made to suit any desiredapplication.

The invention is further illustrated but not limited by the followingexamples in which parts are given by weight unless otherwise specified.

EXAMPLE 1 ethylene glycol was then added and the agitation continued for45 minutes. The resulting prepolymer was a light amber liquid having aviscosity of Z-4.

(B) An isocyanate-terminated prepolymer was prepared by charging into areaction vessel equipped with a stirrer and heating means 130 parts of1,3-butylene glycol, 1950 parts of 2,4-tolylene diisocyanate, and 400parts of trimethylolpropane. The mixture was agitated for 480 minutes at170 F. The resulting prepolymer was a light amber liquid having a lowviscosity.

(C) 100 parts of Prepolymer A and 20* parts of Prepolymer B were mixedwith 100 parts of water, and the resulting compound was used to laminatecotton to acetate at room temperature.

EXAMPLE 2 The procedure of Example 1A was repeated except that theformulation also included 33 parts of trimethylolpropane. The productwas a clear liquid having a medium viscosity.

100 parts of this prepolymer were mixed with 40 parts of the prepolymerof Example 1B and 60 parts of water and used to bond cotton to acetatetricot.

EXAMPLE 3 The procedure of Example 2 was repeated except that thecondensate was 980 parts of a 50/50 mixture of thepolyoxypropylene-polyoxyethylene polyols containing, respectively, 20%of ethylene oxide and 40% of ethylene oxide; the amount of tetraethyleneglycol was 240 parts; and the amount of trimethylolpropane was 9 parts.The product was a clear liquid having a medium viscosity.

EXAMPLE 4 The procedure of Example 2 was repeated except that thecondensate was 900 parts of a 50/50 mixture of the polyols containing,respectively, 20% of ethylene oxide and 30% of ethylene oxide; theamount of tetraethylene glycol was 190 parts; and the amount oftrimethylolpropane was 9 parts. The product was a clear liquid having amedium viscosity.

EXAMPLE 5 (A) The procedure of Example 2 was repeated except that thecondensate was 1750 parts of a 40/ 40/ 20 mixture of polyols containing,respectively, 20%, 30%, and 40% of ethylene oxide; the amount oftetraethylene glycol was 360 parts; and the amount of trimethylolpropanewas 12 parts. The resulting prepolymer was a clear liquid having amedium viscosity.

(B) An NCO-terminated prepolymer was prepared by the process of ExampleLB except that the forrrnulation was 75 parts of butylene glycol, 450parts of trimethylolpropane, 2020 parts of tolylene diisocyanate, and850 parts of ethyl acetate. The resulting prepolymer was a slightlyamber liquid having a low viscosity.

(C) 100 parts of Prepolymer A, 10 parts of Prepolymer B, and 100 partsof water were mixed and used to laminate cotton to acettae tricot.

EXAMPLE 6 The procedures of Examples 1A and 2 were repeated except thatthe glycol was 1,3-butylene glycol. The products were comparable.

6 EXAMPLE 7 The procedure of Example 1A was repeated except that theglycol was dipropylene glycol. The product was comparable.

EXAMPLE 8 The procedure of Example 1A was repeated except that theglycol was a 50/50 mixture of tetraethylene glycol and dipropyleneglycol. The product was comparable.

EXAMPLE 9 The procedure of Example 1A was repeated except that theglycol was tripropylene glycol. The product was comparable.

EXAMPLE 10 The procedures of Examples 1A and 2 were repeated except thatthe glycol was 1,6-hexanediol. The products were comparable.

EXAMPLE 11 The procedure of Examples 1A and 2 were repeated except thatthe glycol was diethylene glycol. The products were comparable.

EXAMPLE 12 The procedures of Examples 1A, 2, and 3-11 were repeated witheach of the following isocyanates instead of tolylenediisocyanatezxylylene diisocyanate, hexarnethylene diisocyanate, analiphatic diisocyanate derived from the diamine of a dimer acid (DDIdiisocyanate), and p,p-diphenyl methane diisocyanate. The products werecomparable.

EXAMPLE 13 The procedure of Example 2 was repeated with each of thefollowing crosslinking compounds instead of trimethylolpropane:triethylolpropane, pentaerythritol, 1,2, 4-butanetriol, sorbitol, andglycerine. The products were comparable, except that they had higherviscosities.

EXAMPLE 14 The procedure of Example 1A was repeated with each of thefollowing catalysts instead of tetramethylbutane diamineztriethylamine,dimethylstearyl-amine, dibutyltin dilaurate, dibutyltin diacetate,stannous octoate, and stannous oleate. The results were comparable.

EXAMPLE 15 The procedure of Example 10 was repeated except that thefollowing pairs were bonded to each other instead of cotton to acetate:cotton/cotton, cotton/nylon, acetate/ acetate, wool/ acetate,wool/nylon, nylon/ acetate, and acrylic fabric/acetate. The results werecomparable.

EXAMPLE 16 The wash resistance of laminates was determined by thefollowing procedure: Strips (1" x 3") were washed five times at 30minutes each in soapy water at F. The peel strength was measured on thewet strips.

The dry cleaning resistance of laminates was determined by the followingprocedure: Strips (1" x 3") were subjected to five 30-minute drycleaning cycles in cleaning solution which consisted of a standard soapyperchloroethylene solution. The peel strength of each laminate wasmeasured wet.

The results of the tests are expressed in peel strength, the pounds perinch required to peel apart one lamina from another across a 1-inchwidth by means of an Instron tester. In each of the following tests theOH-terminated prepolymer was mixed with the NCO-terminated prepolymerand water, and the product was applied to materials as described inExample 1C.

TABLE Peel strength, pounds per inch Parts of Product of examplesprepolymer Coating After B/100 parts of lev automatic After NCO-prepolymer A ounee home 6 dry OH-terminated prepolymer terminated and100 parts square As applied launderings cleanings A prepolymer of wateryard (dry) (wet) (wet) Control 1 0. 39 1.12 0.28 0.35 2 30 0. 40 1. 850. 30 0. 53 30 0. 90 2. 47 0.34 0. 68 0.42 1.55 0.44 0.36 20 0.39 1. 070.38 0. 40 20 0.52 1. 60 0. 46 0.56

Control=a conventional polyester-typo polyurethane adhesive (SunChemical Corporations Warcol'lcx l9 As can be seen above, the productsof this invention had better resistance to washing and to dry cleaning,as indicated by higher peel strengths, than did the control.

In all cases the systems prepared with the polyether polyurethaneprepolymers of this invention were much whiter than that using theconventional polyester polyurethane adhesive and resulted in laminatesthat had superior overall properties.

EXAMPLE 17 A polyester-based urethane system consisting of 20 parts ofthe NCO-terminated prepolymer of Example 5B, 100 parts of theOH-terminated prepolymer of Example 2, and 100 parts of water was usedin an amount of 0.04 ounce/square yard to coat paper. The product was asmooth clear coating.

EXAMPLE 18 The procedure of Example 17 was repeated except that thesubstrates were 2- to 4-mil nylon, Mylar, acetate, leather, and vinylchloride films. The products were smooth clear coatings.

Although the invention has been described in considerable detail in theforegoing, it is to be understood that such detail is solely for thepurpose of illustration and that many varations can be made by thoseskilled in the art without departing from the spirit and scope of theinvention except as set forth in the claims.

What is claimed is:

1. A polyurethane adhesive composition comprising about 40 to 90 percentof (1) the reaction product of a hydroxyl-terminated prepolymer (A)having a molecular weight of about 3500 to 60,000 and anisocyanate-terminated prepolymer (B) having a molecular weight of about300 to 1600 wherein (A) is the product of the stepwise reaction of (a) apolyoxyethylene-polyoxyalkylene glycol condensate with (b) an organicpolyisocyanate and (c) a glycol and (B) is the reaction product of (f) aglycol having a molecular weight of about 62 to 800 with '(g) a polyolhaving a functionality of at least 3 and (h) an organic polyisocyanate,and about 10 to 60 percent of (2) water.

2. The composition of claim 1 wherein the ratio of (1):(2) is about 50to 85 percent:about to 50 percent.

3. The composition of claim 1 wherein the ratio of prepolymer (B):prepolymer (A) is about 10 to 60 parts: 100 parts.

4. The composition of claim 1 wherein the prepolymer (A) is furtherreacted with (d) a polyol having a functionality of at least 3.

5. The composition of claim 1 which additionally contains a catalyst.

6. The composition of claim 4 wherein the prepolymer (A) contains up toabout 8 equivalents of glycol (c) and about 0.05 to 1 equivalent ofpolyol ((1) per equivalent of polyol (a) and sufiicient isocyanate (b)to give a final NCO/OH ratio of about 0.88-0.97 and the prepolymer (B)contains about 3-6 parts of glycol (f), 4-40 parts of polyol (g), and20-60 parts of isocyanate (h).

7. The composition of claim 4 wherein the prepolymer (A) contains about1.5-2.5 equivalents of glycol (c) and about 0.15-0.35 equivalent ofpolyol (d) per equivalent of polyol (a) and the prepolymer (B) containsabout 3-5 parts of glycol (f), 10-15 parts of polyol (g), and 40-60parts of isocyanate (h).

8. The composition of claim 4 wherein the isocyanate (b and h) is2,4-tolylene diisocyanate, the glycol (c) is tetraethylene glycol, thepolyol (d and g) is trimethylolpropane, and the glycol (f) is1,3-butylene glycol.

9. A polyurethane coating composition comprising about 40 to percent of(1) the reaction product of a hydroxyl-terminated prepolymer (A) havinga molecular weight of about 3500 to 60,000 and an isocyanate-terminatedprepolymer (B) having a molecular weight of about 300 to 1600 wherein(A) is the product of the stepwise reaction of (a) apolyoxyethylene-polyoxyalkylene glycol condensate with (b) an organicpolyisocyanate and (c) a glycol and (B) is the reaction product of (f) aglycol having molecular weight of about 62 to 800 with (g) a polyolhaving a functionality of at least 3 and (h) an organic polyisocyanateand about 10 to 60 percent of (2) water.

10. The composition of claim 9 wherein the prepolymer (A) is furtherreacted with (d) a polyol having a functionality of at least 3.

References Cited UNITED STATES PATENTS 3,539,482 11/1970 Stewart 26029.23,410,817 11/1968 McClellan 26029.2 3,442,842 5/1969 Von Boniu 26029.23,522,199 7/1970 Keberle et al 26029.2

DONALD E. CZAI A, Primary Examiner H. S. COCKERAM, Assistant ExaminerUS. Cl. X.R.

2602.5 BE, 7.5 AM, 858

